Burner controls



June l1, 1968 Filed Oct. 22, 1965 A. A. MARKS ETAL BURNER CONTROLS 8 Sheets-Sheet 1 FIGJ IIIHIIIHIIIIIHI IIIIIIIIIIIHIIIII ATTORNEY.

8 Sheets-Sheet 2 TCHOMETER v 3mm Alexander/4511i@ /lar/Kv AMMETER Ii `on. nessuna FIG. 5

A. A. MARKS ETAL BURNER CONTROLS NELTING OVERLDAD TOHOIETER ENGINE OIL PRESSURE STARTING SVIIWH June ll, 1968 Filed oct. 22, 1965 FIG. Z

Saman June ll, 1968 A. A. MARKS ETAL BURNER CONTROLS Filed Oct. 22, 1965 8 Sheets-Sheet 5 l//////////////////{///////////////////(e 3mm F|G 3 Zezmm/er sa/r Mir/Ks JF-On F'rJiZ mm www 777m Snow,

June ll, 1968 A. A. MARKS ETAL BURNER CONTROLS Filed Oct. 22, 1965 www 8 Sheets-Sheet 4 INVENTORS. ALEXANDER ASHTON MARKS JOHN A. FRITZ ATTORNEY.

Juneu, 196s A. A. MARKS ETA.. 3,387,603

BURNER CONTROLS Filed Oct. 22, 1965 8 Sheets-Sheet 5 62' 263 ,262" l262'" |59' leo i insa" lso' @-215 immuni lmmwu INVENTORS.4 ALEXANDER ASHTON MARKS JOHN A. FRITZ ATTORNEY,

June ll, 1968 A. A. MARKS ETAL 3,387,603`

BURNER CONTROLS Filed oct. 22. 1965 e sheets-sheet e O in lel' i leo lea" 96 jl l G I Il FIG. 8

INVENTOR ALEXANDER ASHTON MARKS JOHN A. FRITZ ATTORNEY.

June l1, 1968 A. A. MARKS ETAL 3,387,603

BURNER CONTROLS Filed Oct. 22, 1965 8 Sheets-Sheet 7 mvENToRs. $2' ALEXANDER AsHToN MARKS JOHN A. FRITZ ATTOR NEY.

June 11, 1968 A. A. MARKS ETAL BURNER CONTROLS 8 Sheets-Sheet 8 Filed Oct. 22, 1965 United States Patent O 3,387,603 BURNER CNTROLS Alexander Ashton Marks, Philadelphia, and John A. Fritz,

Ridley Park, Pa.; said Fritz assigner to McKee & Mc- Haie, Inc., Darby, Pa., a corporation of Pennsylvania Filed Oct. 22, 1965, Ser. No. 501,301 23 Claims. (Cl. 126-3435) ABSTRACT GF THE DSCLOSURE A burner control assembly comprising `a burner having a main fuel valve, a main fuel outlet, a pilot fuel valve, a pilot fuel outlet, an electrically operated ignitor disposed in the vicinity of the pilot fuel outlet, and a ilzune monitor adapted to indicate electrically whether a llame is present in the vicinity of the pilot fuel outlet. Relay coils are connected to and energized by a source of current for controlling the operation of the main fuel and pilot valves. When the llame monitor indicates the presence of a llame in the vicinity of the pilot fuel outlet, and when relay control is closed then full speed operation of air blower and full fuel flow is established, and when relay control is open reduced speed of air blower operation and reduced fuel flow is effected. The application of the burner control to an engine depending upon electrical current for its operation and adapted to the operation of a snow melter is described and illustrated.

Our invention relates to burner controls, and it relates more particularly to such controls as applied for instance in snow melters such as those used in snow disposal units.

Snow disposal units containing a snow melter must of necessity be capable of dependable performance under rugged and adverse weather conditions. Moreover, they must themselves generate the heat and power required for their performance. Since breakdowns in oper-ations can be costly and are often capable of resulting in substantial losses arising from failure to remove the snow, it is important that the snow removal units be provided in such a manner as to reduce to a minimum the possibility of such breakdowns.

One object of our invention therefore is to provide a snow melting unit comprising a lburner assembly which is rugged and dependable in operation, and capable of withstanding the adverse conditions which are frequently encountered in snow removal.

Another object of our invention is to provide a sno-w melting unit comprising a burner control in which the possibility of breakdown of the heating system is reduced to a minimum.

A further object of our invention is to provide a snow melting lunit comprising a burner control in which known causes of breakdown are anticipated and avoided.

Another object of our invention is to provide a snow melting unit wherein optimum operating conditions are established despite the rigorous circumstances under which the unit may be required to operate.

A further object of our invention is to provide a burner control wherein heating system breakdown-causing circumstances are avoided despite human failure in complying -with the requirements for optimum performance.

Another object of our invention is to provide a snow removal unit comprising a snow melter of such a nature as to enable the operator to remain within the warmth and safety of the cab a maximum portion of the time during the operation of the unit.

A further object of our invention is to provide a snow removal unit wherein man-hours utilized in its operation,

3,387,603 Patented June 11, 1968 ice supervision, maintenance and repair, are reduced to a minimum.

AFurther objects will appear from the more detailed description which follows.

For the purpose of illustrating our invention, we have shown in the accompanying drawings forms thereof which are at present preferred by us, since the same have been found to give satisfactory and reliable results, although it is to be understood that the various instrumentalities of which our invention consists can be variously arranged and organized, and that our invention is not limited to the precise arrangements and organizations of the instrumentalities as herein shown and described.

Referring now to the drawings in which like reference characters indicate like parts:

FIGURE 1 represents a side elevational view illustrating a snow disposal unit comprising a snow melter having a burner control essembly embodying our invention.

FIGURE 2 represents a fragmentary side elevational view illustrating a snow disposal unit comprising a snow melter having a burner control assembly embodying our invention.

yFIGURE 3 represents an enlarged vertical sectional view illustrating a portion of a snow melting means comprising a burner in a tank, and embodying our invention.

FIGURE 4 represents a vertical sectional view illustrating float switches mounted on a snow melting tank, and embodying our invention.

'FIGURE 5 represents a plan view illustrating controls in the cab of a snow disposal unit embodying our invention.

FIGURE 6 represent a side elevational view illustrating the control current generator, fuel pump and tank, blower engine and blower portions of ra snow melter in a snow disposal unit embodying our invention.

FIGURE 7 represents an end elevational view of the apparatus illustrated in yFIGURE 6.

FIGURE 8 represents an end elevational view of the fuel manifolds of a snow melter in a snow disposal unit embodying our invention.

FIGURE 9 `represents the burner portion of the control circuits in a snow melter embodying our invention.

IFIGURE 10 represents another portion of the control circuits in a snow melter embodying -our invention.

FIGURE 1'1 represents replaceable -control `panels on which are mounted circuitry in a snow melter part of a snow disposal unit embodying our invention.

According to our invention, we provide any suitable snow disposal unit such for instance as the unit designated as A, and which may include a chassis 10 comprising a frame 11, mounted on wheels 12 which may comprise steer-type wheels 12', and drive wheels 12" operated by an automotive engine 13. A suitable snow gathering and conveying means, such for instance as the snow blower mechanism 15 may be mounted on the forward end region of the chassis 10, and may be of any desired construction. Thus it may comprise an intake region such as the intake 16 in which is disposed rotary cutters such for instance as the spiral conveyor blades 17 adapted to cut the snow and convey it to a suitable impeller 18 disposed behind the cutter and conveyor blades 17, and immediately beneath the inlet portion 45 of a suitable chute 19. The chute 19 is adapted to receive snow from the impeller 18 and to direct it to any suitable location, such for instance as the snow melting tank 75.

In a preferred form, the tank is associated with snow melting means 76 which may include downwardly projecting burners 77, 77' and 77".

The snow melting means 76 preferably comprises an engine-operated air blower having a discharge duct system 91 leading to the air intake 92 of each of the 3 burners 77, 77' and 77". Each burner 77, 77', 77 is preferably equipped with one or more fuel nozzles 93, a pilot nozzle 94 and a suitable ignition system comprising an electrode 95. The fuel nozzles 93 and pilot nozzles 94 of each burner 77, 77 77 are disposed in a suitable combustion chamber 100. Passages 134 are preferably provided for conveying a flow of air from the air intake 92, and about the combustion chamber 100, in a manner to absorb heat therefrom. In a preferred form, each of the burners 77, 77 and 77 is provided with a ame monitor 102 adapted to react electrically whenever a flame is present or ceases within the combustion chamber 100.

Each burner 77, 77 and 77 comprises a discharge vent 101 through which heated air under pressure, and hot products of combustion, are emitted.

In a preferred mode of operation, water is initially introduced into the tank 75 until the water level 103 has attained suicient elevation to assure the submergence of the burner discharge vents 101. Snow thereafter emitted through the chute discharge outlet 66 will be distribu-ted throughout the length of the body of water 109 in the tank 75.

When the air blower 90 is in opera-tion, and combustion of fuel is taking place in the burners 77, 77' and 77", a steady stream of pressurized air heated by the burners together with hot products of combustion, is emitted downwardly through the discharge vents 101 of the burners 77, 77' and 77, into the body of water 109.

In a preferred form, means are provided for establishing the water level 103 at a height best suited for optimum performance. Thus, an outlet 104 may be disposed within the tank 75 in a manner to establish a predetermined water elevation 103 above the bottom 81 of the tank 75. A suitable water pump 105 may if desired be connected to the outlet 104, operable to pump water from said outlet 104 to a discharge outlet 106. The water pump 105 may be actuated automatically by means of a float switch 108 actuating a magnet clutch 10S deriving motion from the engine 129 which operates the blower 90.

The float switch 108 may be mounted in a suitable container 123 having a base 124 on which the float switch 108 is mounted, a top 125, a bottom 126, and an inward wall 127 as well as side walls 12S. The base 124, side walls 128, top 125, bottom 126 and inward wall 127 define a chamber 123 in which the float 108" of the float switch 108 is adapted to operate. The bottom 126 of the chamber 123' contains a port 126', and the top 125 contains a vent 125.

A similar float switch 135 may be similarly mounted on the base 124 with its float 135 disposed in the chamber 123 at an upper water level of safe operation of the snow melting unit. The upper float switch 135 may be connected to a suitable alarm such as a flashing light 136, bell 269 or the like disposed among the master controls 36 in the cab 37 to warn the operator to reduce the speed of snow delivery, or to bring the vehicle to a halt and thereby prevent further conveying of snow to the interior of the tank 75. In addition, means may be provided as hereinafter set forth, for stopping the operation of the burners 77, 77' and 77", thereby to prevent the possibility of improper combustion resulting from the increased head pressure of the water in the tank interfering with the air flow from the blower to the burners. The container 123 may be mounted in any suitable location in the interior of the tank 75, such for instance as on the wall 78 or 78 as shown, and may be disposed within the trough 110 as illustrated in FIGURE 4.

In operation, the tank 75 is initially supplied with water to the starting level 103. When the snow melter is in operation, the blast of hot products of combustion and heated air directed downwardly through the discharge vents 101 of each of the burners 77, 77 and 77", is deflected outwardly and upwardly by the bottom 81 of the tank 75, and in so doing disturbs the surrounding water in a manner to create great agitation thereof.

As the snow melts however water is thus added to the water initially placed in the tank 75, and its nominal level will have increased beyond the starting water level 103. Such water enters the ports 126 of the float switch container 123 and rises in the chamber 123 according to hydrostatic pressure. The float 108" is accordingly made to rise and to actuate the switch 108 and thus to actuate the pump 105. Should the increase in volume of water within the tank exceed the capacity of the pump to expel the excess water therefrom, or should the pump be manually disconnected as for instance when it is desired not to discharge water from the tank 75, the upper limit 103 of safe operation may be reached. The hydrostatic pressure having thus impelled the water in the chamber 123 to reach and to lift the valve float 135', the float and switch 135 is actuated to initiate the stopping of further introduction of snow into the tank 75.

In a preferred form, a primary burner control device 151, 151 and 151 is used respectively with each of the burners 77, 77' and 77 and may be of the type commercially available under the registered trademark Protcctorelay. Each of these control devices may comprise electric switches responsive to signals relating to the operation of the burner with which it is associated, said switches being adapted to participate in the control of devices utilized in the operation of said burner. Thus by way of example, the flame monitor 102 of the burner 77 may be connected as at 152 and 153 to the primary control device 151, the primary coil of an ignition transformer 154 may be connected to said control device as at 156, the secondary coil of said transformer 154 being connected to the electrode of said burner 77, and the pilot valve 99 may be connected as at 156 to said primary control device.

A common power line 157 may be connected, by means of the manual switch 158, included among the master controls 36 in the cab 37, to the primary burner control device 151, as at 164, and also to the pilot valve 99 and to the primary coil of the ignition transformer 154. A series of relays 159 and 160 may be interposed between the primary burner control device 151 and a hot power line 162. Switches controlled by the relays 159 and 160, may be connected to the fuel supply valve 97 and to a suita-ble throttle device such for instance as the throttle solenoid 163 adapted to control the speed of the air blower 90.

In like manner, the primary burner control device 151 may be connected to the flame monitor 102', ignition transformer 154', pilot valve 99', and the common line 157, by means of a manual switch 158 included among the master controls 36 in the cab 37, and to the hot power line 162 by means of a series of relays 159 and 160 similarly related to the fuel supply valve 97' and throttle solenoid 16S-all of the foregoing being associated with the operation of the burner 77'. Similarly, the primary burner control device 151" may be connected to the following associated with the operation of the burner 77: flame monitor 102, ignition transformer 154, pilot valve 99, manual switch 158" among the master controls 36 in the cab 37 and leading to the common line 157, and relays 159 and 160 leading to the hot power line 162 and similarly related to the fuel supply valve 97" and throttle solenoid 163.

The current for the common power line 157 and hot power line 162 may be supplied by any suitable source of volt A.C. current, such for instance as the generator 165, or an invertor (not shown).

The generator 165 is preferably of the load starting and maintaining type, and is adapted to become actuated on the imposition of a load 166 by the closing of a relayoperated switch 167, and to be de-activated when said switch 167 is opened. In a preferred form, a main fuel pump 177 is operated in any suitable marmer as for instance by the generator shaft 178, or (not shown) by the engine 129, and is connected at one end to a fuel storage tank 179, and at the other to a suitable fuel manifold 189 adapted to feed fuel under pressure to separate fuel control assemblies 181, 181' and 181", for each of the respective burners 77, 77 and 77 Each fuel control assembly preferably comprises a fuel pressure regulator 182, 182', 182", a pilot valve such as the valves 99, 99

99" and a fuel supply valve such as the Valve 97, 97', 97".

A fuel return 183 leads from the fuel pressure regulators 182, 182' and 182" back to the fuel storage tank 179 operably to return to the tank all fuel pumped therefrom which is not being fed through the pilot valves 99, 99

99" and the supply valves 97, 97', 97".

The relay-operated switch 167 is preferably' part of a system of controls associated with the operation of the air blower engine 129, and is preferably adapted to be open at all times unless all of the following conditions are met:

(a) The blower engine ignition system 1s on, whether by the starter switch 169 being turned on, or by the engine 129 being in actual operation.

(b) The blower engine 129 has warmed up suicieiitly, for instance to a temperature of 140 F., to enable the engine 129 to continue operation at a full load.

(c) The blower 96 has been operated by the engine 129 sufficiently to establish enough air pressure to supply the air requirements of the pilot flames of all the burners 77, 77', 77".

(d) There is sufficient oil pressure in the engine 129 to permit proper performance of the engine.

(e) The engine has not overheated, i.e. its temperature has not reached a predetermined degree that is inconsistent with safe performance thereof.

(f) The manual stop switch 170 among the master controls 36. in the cab 37, is open.

(g) Any emergency stop switch, such for instance'as the manual switch 171 in the vicinity of the engine 129, is open.

Thus, as long as the operation of the generator 165 or invertor is dependent on the relay-operated switch 167, control current will be supplied only when the blower engine 129 is operating and the blower 90 is maintaining sufficient air pressure to maintain pilot flames at all of the pilot nozzles 94 when the blower engine 129 is operating at throttled speed.

Current thus established is preferably connected by means of switches hereinafter described, to the common line 157 and the hot line 162. Control circuits 198, 198', 198" respectively relating to the burners 77, 77 and 77" are connected to the common line 157 and the hot line 152 through the respective primary control devices 151, 151', 151".

The source of control current, air blower 90 and burners 77, 77', 77", together with their respective parts, switches and controls, are so related that when the following conditions are present:

(a) the aii blower 90 is in operation at the required speed to supply the proper amount of air to maintain a pilot flame in the burner 77,

(b) the relay operated switch 167 is closed,

(c) the source of control current such as the generator 165 is on, and

(d) the manual switch 158 is closed,

the following will occur iii the circuit 198 with respect to the burner 77:

A. Common line current will be supplied:

(l) to the primary burner control device 151;

(2) to the pilot valve 99; and

(3) to one end of the primary coil of the ignition transformer 154.

B. Common line current Will also be supplied to one end of each of the coils 172 and 173 of the respective relays 159 and 168, the relay coils 172 and 173 hereinafter being sometimes referred to respectively as relay coil A and relay coil B.

C. Hot line current will be supplied by the hot feeder line 162:

( l) to the other end of the relay coil 172, thereby energizing it and closing its normally open switches 188, 189, and opening its normally closed switch 196 and (2) also as 175 and 176 to the primary burner control device 151, which in turn supplies said current to tbe pilot valve 99 and to the other end of the primary coil of the ignition transformer 154;

D. The electrode will thus be energized by the ignition transformer 154, delivering a spark in the pilot flame zone 184.

E. The pilot valve 99 will open, allowing fuel under pressure from the fuel pump 177 to be emitted in atomized form through the pilot nozzle 94, in the presence of the spark delivered by the electrode 95, thus igniting the pilot flame.

F. The pilot llame being ignited, the flame monitor 102 becomes energized, thereby closing the appropriate switch (not shown) in the primary burner control device 151, thereby allowing it to pass hot line current through the terminal 199, to the other end of the relay coil 173 of the relay 160, thereby energizing said relay and thus closing its normally open switches 185 and 187.

G. The normally open switch i187 and the normally closed switch 196 are in series with the hot line 162 and, via circuits 198', 198" controlling the remaining burners, with a hot return line 197 which thus feeds hot current to the normally open switches 188 and 189 which have been closed by the energizing of the coil 172.

The circuitry of the circuits 198 and 198" is such that hot line current thus fed thereinto will also be fed to the hot return line 197 regardless of whether the manual switches 158' and 158 are open or closed, Ias long as no malfunction occurs in the burners 77, 77', 77".

H. The closing of the switch 189 to which hot line current is thus being fed, opens the throttle 163 of the blower engine 129 thereby immediately increasing the speed of the blower 90 and thus increasing the air supply to an amount sufcient for the proper combustion of the fuel supplied to each burner, plus an additional supply of Vair to be heated by the burning fuel in the heating apparatus.

I. The closing of the switch 188 to which hot line current is thus being fed, simultaneously opens the main llame supply valve 97, thereby allowing fuel under pressure from the fuel pump 177 to be emitted in atomized form through the main llame nozzle 93 in the presence of the pilot flame which is being monitored by the llame monitor 102.

I. The energizing of the relay closes a normally open switch leading to a signal light 186 in the cab 37, the illumination of said light indicating a pilot llame is actually present in the burner 77.

Should llame cease to exist in the combustion chamber, for whatever reason, the ame monitor 182 will cease to be energized and hot line current will be cut off from the terminal 199 and hence from the relay 160. The relay coil 173 being thus deenergized, the switches 185 and 187 are released to their normally open condition. Since the switch 196`is also in open condition because the relay coil 172 still continues to be energized, hot line current is thus cut off from the hot return line 197 which feeds current to the fuel supply valve 97 and air blower engine throttle solenoid 163, by means of the respective relay switches 188 and 189. The fuel supply valve 97 is thus shut off, and the air blower engine is reduced to throttle speed.

At the same time de-energization of the coil 173 also results in opening the switch l'185 thereby turning out the signal light 186 in the control cab 37, and thus informing the operator that the burner 77 is not functioning.

On the other hand, in the operation of turning on the burner (as for instance by closing the manual switch 158), should the pilot ame fail to ignite, it will be found that the relay 159 will nonetheless be energized. However, because no flame exists in the combustion chamber 100, the llame monitor 102 will not have been energized, and therefore no hot current will be fed to the relay 16S. Nonetheless, hot line current will continue to be fed through the hot feeder line 1162 to the primary burner control device 151, and thus to the pilot valve 99 and electrode energizing transformer 154, thereby continuing the effort to establish a pilot flame in the combustion chamber 106. But because the relay `160 has not been energized, the switch 185 will remain open, and the signal light 186 in the cab 37 will not be on. Thus the operator will be advised that the burner is not functioning.

Similarly, when the operator in the cab 37 begins operations, the signal light 186 is dark, and will continue to be dark until a ame actually exists in the combustion chamber 106i. Thus, the operator is advised at all times, of the presence or absence of a flame in the combustion chamber 100.

In substantially the same manner, when the relay switch 167 is closed (the air blower 90 being at proper speed to maintain the pilot ame), the generator 165 or invertor is 011, and either or both the manual switch 158' or 158" are closed, the corresponding burners 77' and 77 will operate and their respective signal lights 186' and '186" will indicate the presence or absence of ame in their respective combustion chambers. In the case of the circuits 198' and 198", however, the hot: line current is supplied by means of a jumper line 262 between the circuits 198 and 198', and 'the jumper line 203 between the circuits 198' and 19S".

In a preferred fonn, current is constantly fed from the hot line 162 to the pole 204 of the switch 196 operated by the relay 159, and to the pole 205 of the switch 137 operated by the relay 160; and the jumper line 282 is connected at one end, to the normally closed terminal 206 of said switch 196, and to the normally open terminal 207 of said switch 187, and at the other end to the pole 204 of switch 196 operated by the relay 159', and to the pole 205 of switch 187' operated by the relay 160. In a similar manner, the jumper 203 is connected at one end to the normally open terminal 297 of switch 187', and to the normally closed terminal` 206' of switch 196'; and at the other end to the pole 204" of switch 196" operated by the relay 159", and to the pole 205" of switch 187 operated by the relay 160". Also in a preferred form, the normally closed terminal 206" of switch 196", and the normally open terminal 207" of switch 187" are connected to the hot return line 197.

With the exception of the derivation of hot line current being fed to the poles 264, 205 and their corresponding poles 2li-1t', 265', and 284", 295", and also the connection of terminals 206", 207" to the hot return line 197, the circuitry of each of the circuits 198' and 198" is substantially identical to that of circuit 198.

Moreover, each of the burner circuits 198, 198', 198", to a substantial degree operates independently of the remaining burner circuits.

In a preferred form such as that illustrated in the drawings, the circuits are so arranged that the operator is enabled to select the burner or burners which he wishes to use, by turning on the switches 158, 158', 158" corresponding to the selected burners, the blower engine 168 being started by turning on the starter switch 169. In this way with respect to the remaining burners which are not to be used, no current is passing to their respective pilot valves 99, 99', 99" or to their respective ignition transformers 154, 154', 154", and no fuel or current is wasted in said burners.

On the other hand, should the iiame in any burner become unintentionally extinguished, the de-energization of the relay 160, 160', 160" corresponding to said burner will open the corresponding switch 187, 187', 137", thereby shutting off this source of hot line current to the following jumpers 202, 203, and the return line 197.

Inasmuch as the relay 1-59, 159', 159" corresponding to the burner in which the flame has been unintentionally extinguished, is still being energized by reason of its respective manual switch 158, 15S', 158" remaining closed, the corresponding switch 196, 196', 196" will remain open. Thus, there is no way for hot line current to by-pass the open switch 187, 187', 137", and all the main fuel valves will be shut down. At the same time, the blower is reduced to throttle speed so that there will be sufficient air to support combustion of the pilot flames, without extinguishing said dames.

he de-energization of the relay 169, 16d", 16S" also opens the respective related switch 185, 185", thereby turning olf the corresponding signal light 156, 156', 186" relative to the burner whose flame has failed. Since the pilot light is on in all the other burners whose switches 158, 158', 158" are closed, the operator is informed at a glance, which burner has failed. He may then open the switch 158, 158', 15S" corresponding to that burner; and by so doing, close the corresponding switch 196, 196', 196, thereby feeding hot line current to the following jumpers 2512, 203, and the return line 197. The remaining burners whose switches 158, 158', 158" are closed, will then resume operation, with fuel being fed through their respective main fuel valves 97, 97', 97", and air being supplied at unthrottled speed by the blower 9G. The air thus supplied -by the blower 90, being fed to all the burners 77, '77', 77" regardless of the presence of liame therein, the air flowing through the burner which has been shut down, tends to purge the interior, of accumulations of hot gases, and unburned fuel. After sucient time is given for this purging, the operator may re-close the switch 15S, 158', 158" corresponding to said burner, and the burner may resume operation.

It is to be understood that an additional burner circuit or circuits, each corresponding to the circuit 198', may be interposed in the jumper line 292 or 203, as desired. Also, lif only two burner circuits are desired, the circuit 198' and jumper 203` may be dispensed with, and the jumper 262 extended instead to connect the circuits 198 and 19S", the connection of the circuit 198" being at the same location as is indicated herein for the jumper 263. Moreover, if itis desired to have only one burner circuit 19S, the hot return line 197 may be connected directly to the circuit 198 in the same manner as the jumper 262 is shown connected with said circuit, and the jumpers 202, 205y and circuits 198 and 19S" may be dispensed with.

Current -is preferably fed to the burner circuits 198, 198' and 198" by means of circuitry which will withhold current from their feeder lines such as the hot line 162, or if desired the common line 157, when the air blower 90 is not producing the proper air supply as hereinabove set forth, or when the blower engine 129 is not functioning properly, or in the event it is desired to stop the operation of said engine; and in a preferred form, said current is generated only when said circuitry permits the feeding of such current to the burner circuits. Such circuitry may be powered by an independent source of current, such for instance as a 12-volt DC. generator 208 operated by the blower engine 129 and having terminals 209 and 210'. A signal light 211 may be disposed among the master controls 36 in the cab 37, and shunted across the terminals 269, 210 of the generator 208 to indicate when the generator is emitting power. Au engine temperature switch 212 and a suitable air pressure switch 213, deriving current from the generator 29S, may be disposed in series with the coil 214 of a relay 215. A normally open switch 216 may be shunted across the terminals of the blower engine starter switch 169, and may be adapted to be closed by the energization of the coil 21d. The normally open switch 167 may also be operated by the relay 215; and said relay may also operate .a switch 264 whose pole may be connected to the terminal 269 when the engine temperature switch 212 and air pressure switch 213 are closed.

The engine temperature switch 212 may be suitably mounted on the engine 129 or its cooling system in a manner to be controlled by the temperature thereof, and may be of the type which is normally open and adapted to be closed when the temperature .attains a degree, such for instance as 140 F., which is consistent with the minimum required for satisfactory operation of the engine 129. The air pressure switch 213 may be suitably mounted on the blower 90 or a part of the discharge duct system 91, and is adapted to be normally open until the air pressure established by said blower 90 has reached a predetermined amount which is consistent with the proper pressure for maintaining pilot flames in all of the burners 77, 77', 77", whereupon the switch 213 will close and remain closed until the pressure established by the blower 90` has fallen below that amount.

The terminal 210 of the l2-volt generator 23S may be connected to a power line 217. A feeder line 218 may be connected to one terminal 219 of a coil 22%` of a relay 221. Another terminal 222 of the coil 22@ may be connected to a normally closed manual switch 223 which is preferably disposed among the master controls 36 in the cab 37. Said normally closed switch 223 may be connected in series with a return line 224 which is connected to the normally open contact 225 of the switch 264.

A normally open switch 226, adapted to be closed upon the energization of the coil 225, may be disposed in series with the return line 224 and with a terminal 227 of an audible alarm such as a buzzer 228 disposed among the master controls 36 in the cab 37. Another terminal 229 of the alarm 228 may be connected to the power line 217.

A normally open switch 230 may be adapted to be closed upon the energization of the coil 22) whereupon it connects the feeder line 213 to the power line 217.

The feeder line 218 may also be connected to the power line 217 by means of any of .additional normally open switches such for instance as the low oil pressure switch 231, engine high temperature switch 232, high-water initiated, delayed action switch 265, burner operated thermal switches 266, 266', 266" and emergency stop switch 171.

The oil pressure switch 231 is disposed in the blower engine 129 and is adapted to be closed when the oil pressure therein falls below a safe limit. The high temperature switch 232 is mounted in a suitable part of the engine 129 or the cooling system thereof and is adapted to be closed when the temperature thereof has reached a limit consistent with safe operation of the engine.

The high-water initiated, delayed action switch 265 may be used in conjunction with the iloat switch 13S operated by the float 135' as illustrated in FlGURE 4. rhe switch 265 may comprise normally open switch members 267, one of which is connected to the p wer line 217, the other being connecte to the feeder line 218-. A heating element 263 may be connected in series with one normally open terminal of the float switch 135 and the terminal 209 of the 12-volt engine generator 208. The other terminal of the float switch 135 may be connected to the other terminal 210` of the generator 268. Suitable warning devices such for instance as the warning light 135 and the audible alarm 269' may be connected in parrllel with the heating element 268, and disposed among the master controls 36 in the cab 37. 1f desired, the switch members 267 may be connected instead, to the terminals 238 and 239, hereinafter described.

The thermal switches 266, 266', 266 may respectively be mounted on a casing of each burner 77, 77', 77", preferably upow of the location of the flame t-herein. The thermal switch 266 may be attached to the casing in any suitable manner (not shown) such as bolts, welding or the like, and is adapted to be operated by elevation of temperature a given degree in the portion of the burner at which it is attached. Thus for instance, should back pressure in the burner cause the frame to ow rearwardly, the thermal switch will operate. By the use of this switch,

the burner is shut down, thereby eliminating possibility of damage to the burner and its component parts. The emergency stop switch 171 may be mounted in the vicinity of the blower engine 129* or in any other desired location where a workman would nd it convenient to stop the operation of the burners by turning off the blower engine when conditions observable exterior of the cab 37 would warrant him in doing so.

Thus, current may be initially fed to the coil 22@ of the relay 221 when either the oil pressure of the blower engine 129 is too low for safe operation, the temperature of said engine is too high for safe operation, the head of water in the tank 75 is too high for proper operation of the burners 77, 77', 77", the temperature upflow of the flame in any burner has risen beyond a proper degree, or a workman has manually closed the emergency stop switch 171. When the coil 220 is thus energized, the switch 226 closes and the alarm 228 sounds in the cab 37, thereby notifying the operator in the cab 37. In addition, energization of the coil 220 closes the relay switch 23) thereby continuing to feed current to the ala-rm 228 until the switch 223 is manually opened by the operator in the cab 37. Opening of the switch 223 disconnects the coil 226, resulting in complete de-energization of the relay 221 and consequent disconnection of the alarm 22S.

A coil 234 of a relay 235 may be connected at one terminal 236 to the return line 224, and at another terminal 237 to a terminal 238 of the normally open stop switch 170 located in the cab 37. The opposed terminal 239 of the stop switch 176 is connected to the power line 217. A normally open switch 240 operated by the relay 221, is connected in a manner to shunt the normally open stop switch 1713 when the relay coil 220 is energized, and to be opened upon the de-'energization thereof.

A normally open switch 241 is connected at one terminal to the power line 217 and at another terminal to the terminal 237 of the relay coil 234. Thus the relay 235 is energized upon any of the alarm or stop actuating occurrences relating to the circuits connected with the switch 264 when said switch is in closed condition, and remains energized until the blower engine 129 has come to a stop, thereby ceasing the operation of the l2-volt generator which energizes the relay 215 which holds the normally open switch 264 in closed condition.

A normally closed switch 242 is adapted to be open when the coil 234 of the relay 235 is energized, and is connected in series with the hot line 162 of the control circuits 198, 19S', 198" and with the hot terminal 243 vof the control current generator 165 or invertor. Thus when the relay 235 is energized, the burner control circuits are disconnected and the main llame valves 97, 97', 97", and pilot valves 99, 99', 99 are all shut off and the ignition transformers 154, 154', 154" are disconnected.

A normally open switch 244 is adapted to be closed when the coil 234 of the relay 235 is energized; and is connected at one terminal 245 to the terminal 243 of the control current generator 165 or invertor, and at another terminal or pole 246 to a stop timer device 247 which is preferably disposed in series with the engine coil 248 and ignition system 249 of the blower engine 129. One such timing device 247 may consist of a thermo-timer comprising a heating element 251B connected at one end to the terminal 246 as aforesaid, and at the other end to a terminal 251 of the control current generator 165 or invertor. A normally closed, thermally operated switch 252 may in any suitable manner be connected in series with the ignition -coil 248 and the ignition system 249, and disposed in the vicinity of the heating element 25@ in a manner to be opened following the energization of the heating element 250 and closed after heat is no longer emitted thereby. In a preferred form, when the heating element 256B is energized, the generation of heat therein and the reaction of the switch 252 thereto involves a time lag of approximately ninety seconds, and when the heating element 250 no longer receives current from the generator 165,

the response of the switch 252 involves a` delay in reclosing said switch such as to impose an additional time lag of preferably two minutes. Thus, when any of the alarm or stop actuating switches relating to the blower engine 125 is closed, the ignition coil 243 will become disconnected so as to bring said engine to a stop, but this stop will not occur until a time lapse such for instance as ninety seconds; and when it is desired to restart the blower engine 129 it will not be possible to do so until a further lapse of time such for instance as two minutes, will have occurred. By this means, whenever the blower engine 129 comes to a stop by the closing of any of the switches 171), 171, 231, 232, 265, 266, 266', 266", the pilot and main flame valves feeding oil into the burners '77, 77', 7 7 will become immediately closed and the arne ignition electrodes immediately disconnected, but the blower Si@ will continue to function for a predetermined time, such for instance as ninety seconds, thereby purging each of said burners, both removing therefrom products of combustion and reducing the temperature of the burners to a degree below the temperature at which oil would ignite when the pilot valve 99 is again open; and deactivation of the blower engine for an additional two minutes assures such reduction of temperature of said burners. Thus means are provided for preventing re-ignition of flame in the burners 77, 77', 77 without resort to the control circuits 198, 198', 19S".

In a preferred form, the float switch 16S comprises a normally closed switch 27@ and a normally open switch 271; the normally closed switch being disposed in series with the engine starter switch 169 and starter solenoid 272; and the normally open switch being disposed in series with the terminal 215* of the 12-volt engine generator 26S, and one terminal of the magnetic clutch 168', the other terminal of which is connected to the terminal 269 of thc generator 208. in this manner, the blower engine 129 is prevented from being started when the water level in the tank '75 is higher than the desired level 133. Moreover by this means, when the head of water exceeds the desired level 103 after the engine 129 has been started, the magnetic clutch 108 connects the pump 105 with the engine 129, operably to pump the excess water out of the tank.

ln one preferred form, means are provided for utilizing the control current generator 165 or inverter without operating the burners 77, 77', 77". Thus for instance, a manual double pole switch 253 may be provided, having a normally closed switch 254 connected in series with the normally closed switch 242 and the hot terminal 243 of the generator 165, or invertor, and a normally open switch 255 connected in series with the pole 256 of the normally open switch 167 and the common terminal 251 of the control current generator 165, or invertor. By this means, when the switch 253 is disposed in one position such as that illustrated in the drawings, the control current generator 165 or invertor will operate the burner circuits 198, 198', 153" and when it is in its alternate position the switch 254 will be open thereby disconnecting the burner control circuits 195, 158', 195, and the switch 255 will be closed thereby feeding common current to any desired appliances or other electrical means, such for instance as the lighting means 257 or devices connected to the outlet receptacle 258, said lighting means 257 and receptacle 258 being connected in parallel with the starting load 166. The manually operated switch 253 is preferably disposed in the vicinity of the control current generator 165.

In a preferred form, the relay systems including the primary burner control device, together with the ignition transformer, for each circuit 198, 193', 198 are mounted on ya separate panel 259, 259', 259, and the remaining relay systems are mounted on a separate panel 268. The circuitry in each panel .may be connected by suitable plug and jack systems such as those indicated respectively at 261 and 262, 261 and 262', 261 and 262, 261'" and 262'", to the remainder of the circuitry by means of suitable cables such as those referred to generally as the cables 263. The panels 259', 259 and 259 may be interchangeable. in this manner, should any malfunction occur in any of the controls in the circuits while the snow removal unit is in actual operation, expensive shutdowns can be avoided by simply replacing a control panel, which can be done in a minimum of time, by disconnecting the plug from the jack on that panel, replacing the panel and reconnecting the plug on the jack in the new panel. Servicing of the malfunctioning device can then be achieved at a more convenient time and more practical location for such purpose.

We are aware that the invention may 4be embodied in other specific forms without departing from the spirit or essential attributes thereof, and we therefore desire the present embodiment to be considered in all respects as illustrative and not restrictive, reference being had to the appended claims rather than to the foregoing description to indicate the scope of the invention.

Having thus described our invention, what we claim as new and desire to secure by Letters Fatent is:

1. A burner control assembly comprising:

A burner having a main fuel valve,

a main fuel outlet,

a pilot fuel valve,

a pilot fuel outlet,

an electrically operated ignitor disposed in the vicinity of said pilot fuel outlet,

a llame monitor adapted to indicate electrically whether a flame is present in the vicinity of said pilot fuel outlet;

A blower assembly adapted selectively to convey air at full speed and at reduced speed, to said main fuel and pilot fuel outlets;

A relay coil A connected to and energized by a source of control current having a hot line and a common line;

A normally open switch adapted to be closed by the energization of said relay coil, and disposed in series with said main fuel valve and a feeder line;

A normally open switch disposed in series with said blower assembly and said feeder line, and adapted when closed to establish full speed operation of said blower, and when open to establish reduced speed operation or" said blower, said switch being adapted to be closed by the energization of said relay coil;

A relay coil B connected at one portion of said cornrnon line, and at another portion to a switch controlled by said flame monitor whereby when said flame monitor indicates the presence of a ame in the vicinity of said pilot fuel outlet, connection is made to said hot line, thereby energizing said relay coil B;

A normally open switch adapted to be closed by the energization of relay coil B, and disposed in series with said hotline and said feeder line.

2. A burner control assembly as defined in claim 1,

and further characterized by:

A switch adapted to be operated by the energization of said relay coil B, and connected to a signal.

3. A burner control assembly as defined in claim 1,

o and further characterized by:

Said ignitor and said pilot valve being connected to, and

energized by said source of control current. 4. A burner control assembly comprising: A plurality of burners, each having a main fuel valve, a main fuel outlet, a pilot fuel valve, a pilot fuel outlet, an electrically operated ignitor disposed in the vicinity of said pilot fuel out-let,

i3 a llame monitor adapted to indicate electrically whether a flame is present in the vicinity of said pilot fuel outlet;

A blower assembly adapted selectively to convey air at full speed and at reduced speed, to said main fuel and pilot fuel outlets;

A relay coil A connected to and energized by a source of control current having a hot line and a common line;

A normally open Switch adapted to be closed by the energizatic-n of said relay coil, and disposed in series with said main fuel valve and a feeder line;

A normally open switch disposed in series with said blower assembly and said feeder line, and adapted when closed to establish full speed operation of said blower, and when open to establish reduced speed operation of said blower, said switch being adapted to be closed by the energization of said relay coil;

A relay coil B connected at one portion to said cornmon line, and at another portion to a switch controlled by said flame monitor whereby when said flame monitor indicates the presence of a flame in the vicinity of said pilot fuel outlet, connection is made to said hot line, thereby energizing said relay coil B;

A jumper line;

The relay coil B of one of said burners, having operatably disposed in conjunction therewith, a normally open switch adapted to be closed by the energization of said coil, said switch being disposed in series with said hot line and said jumper line;

Said jumper line being connected to a normally open switch adapted to be closed by the energization of a relay coil B of another of said burners, said lastmentioned switch being disposed in series with said jumper line and said feeder line.

5. A burner control assembly as defined in claim 4 and further characterized by:

The relay coil A of the rst mentioned of said burners having operatably associated therewith a normally closed switch disposed intermediate said jumper and said hot line.

6. A burner control assembly as defined in claim 5,

and further characterized by:

Each of said burners having associated therewith a switch intermediate said common line and said relay coils A and B, and adapted selectively to establish the operation of the burner associated therewith.

7. A burner control assembly as defined in claim 5,

and further characterized by:

A switch adapted to be operated by the energization of said relay coil B, and connected to a signal; Said ignitor and said pilot valve being connected to, and energized by said source of control current.

S. A burner control assembly comprising:

An engine depending upon electrical current for its operation;

An engine-operated source of current deriving power from said engine and adapted to supply electricity thereto;

A burner comprising a combustion chamber having:

an air intake portion, and means to discharge fuel into said chamber;

A blower assembly connected to and operated by said engine, and adapted to supply air under pressure to said intake portion;

A control circuit adapted to control the operation of said burner;

A source of control current adapted to supply current to said control circuit;

Means to supply said current to said control circuit only when predetermined factors are present;

Said last-mentioned means including:

an engine-temperature switch adapted to operate when said engine has attained a normal operating temperature.

9. A burner control assembly comprising:

An engine depending upon electrical current for its operation;

An engine-operated source of current deriving power from said engine and adapted to supply electricity thereto;

A burner comprising a combustion chamber having:

an air intake portion, and means to discharge fuel into said chamber;

A blower assembly connected to and operated by said engine, and adapted to supply air under pressure to said intake portion;

A control circuit adapted to control the operation of said burner;

A source of control current adapted to supply current to said control circuit;

Means to supply said current to said control circuit only when predetermined factors are present;

Said lastamentioned means including:

an air-pressure switch responsive to said air under pressure, and adapted to operate when said pressure is sufficient to support a flame in said combustion cham-ber.

10. A burner control assembly comprising:

An engine depending upon electrical current for its operation;

An engine-operated source of current deriving power from said engine and adapted to supply electricity thereto;

A burner comprising a combustion chamber having:

an air intake portion, and means to discharge fuel into said chamber;

A blower assembly connected to and operated -by said engine, and adapted to supply air under pressure to said intake portion;

A control circuit adapted to control the operation of said burner;

A source of control current adapted to supply current to said control circuit;

Means to supply said current to said control circuit only when predetermined factors are present;

Said last-mentioned means including:

an oil pressure switch adapted to operate when the oil pressure in said engine falls below a safe level.

11. A -burner control assembly comprising:

An engine depending upon electrical current for its operation;

An engine-operated source of current deriving power from said engine and adapted to supply electricity thereto;

A burner comprising a combustion chamber having:

an air intake portion, and means to discharge fuel into said chamber;

A blower assembly connected to and operated by said engine, and adapted to supply air under pressure to said intake portion; f

A control circuit adapted to control the operation of said burner; Y

A source of control current adapted to supply current to said control circuit;

Means to supply said current to said control circuit only when predetermined factors are present;

Said last-mentioned means including:

means to initiate the stopping of said engine, and substantially simultaneously to terminate the supply of current to said control circuit;

Means to delay the stopping of said engine for a suffcient time following the termination of supply of control current, to permit said air under pressure to purge said burner.

l2. A burner control assembly comprising:

An engine depending upon electrical current for its operation;

An engine-operated source of current deriving power from said engine and adapted to supply electricity thereto;

A burner comprising a combustion chamber having:

an air intake portion, and

means to discharge fuel into said chamber;

A blower assembly connected to and operated -by said engine, and adapted to supply air under pressure to said intake portion;

A control circuit adapted to control the operation of said burner;

A source of control current adapted to supply current to said control circuit;

Means to supply said current to said control circuit only when predetermined factors are present;

Said last-mentioned means including:

Means to delay the supply of fuel to said burner subsequent to the termination of supply of control circuit current, until said burner has cooled below fuel-ignition temperature.

13. A burner control assembly comprising:

An engine depending upon electrical current for its operation;

An engine-operated source of current deriving power from said engine and adapted to supply electricity thereto;

A burner comprising a combustion chamber having:

an air intake portion, and

means to discharge fuel into said chamber;

A blower assembly connected to and operated by said engine, and adapted to supply air under pressure to said intake portion;

A control circuit adapted to control the operation of said burner;

A source of control current adapted to supply current to said control circuit;

Means to supply said current to said control circuit only when predetermined factors are present;

Said last-mentioned means including:

an engine temperature switch adapted to operate when said engine has attained a temperature substantially close to the upper limit for safe operation.

14. A burner control assembly comprising:

An engine depending upon electrical current for its operation;

An engine-operated source of current deriving power from said engine and adapted to supply electricity thereto;

A burner comprising a combustion chamber having:

an air intake portion, and

means to discharge fuel into said chamber;

A blower assembly connected to and operated by said engine, and adapted to supply air under pressure to said intake portion;

A control circuit adapted to control the operation of said burner;

A source of control current adapted to supply current to said control circuit;

Means to supply said current to said control circuit only when predetermined factors are present;

Said last-mentioned means including:

a thermal switch adapted to operate when the temperature of the burner upow of the flame is above a normal degree.

l5. A burner control assembly as defined in claim 8,

and further characterized by:

An air-pressure switch responsive to said air under pressure, and adapted to -operate when said pressure is sufficient to support a flame in said combustion chamber;

An oil pressure switch adapted to operate when the oil pressure in said engine falls below a safe level;

Means to initiate the stopping of said engine, and substantially simultaneously to terminate the supply of current to said control circuit;

Means to delay the stopping of said engine for a sufcient time following the termination of supply of control circuit current, to permit said air under pressure to purge said burner;

Means to delay the supply of fuel to said burner subsequent to the termination of supply of control circuit current, until said burner has cooled below fuelignition temperature;

An engine temperature switch adapted to operate when said engine has attained a temperature substantially close to the upper limit for safe operation;

Said last-mentioned means including:

a thermal switch adapted to operate when the temperature of the burner uptlow of the dame is above a normal degree.

16. A snow melter comprising:

A burner assembly having:

An engine depending upon electrical current for its operation;

An engine-operated source of current deriving power from said engine and adapted to supply electricity thereto;

A burner comprising a combustion chamber having:

an air intake portion, and

means to discharge fuel into said chamber;

A blower assembly connected to and operated by said engine, and adapted to supply air under pressure to said intake portion;

A control circuit adapted to control the operation of said burner;

A source of control current adapted to supply current to said control circuit;

A tank adapted to retain water and to receive snow;

Said burner being adapted to heat said water and to melt said snow when said blower assembly is in operation and current is supplied to said control circuit;

Means to supply said current to said circuit only when predetermined factors are present;

Said last-mentioned means including:

A switch adapted to operate when said water has attained a level above normal; and

Means adapted, when said last-mentioned switch is in operation, to prevent starting of said engine.

17. A snow melter comprising:

A burner assembly having:

An engine depending upon electrical current for its operation;

An engine-operated source of current deriving power from said engine and adapted to supply electricity thereto;

A burner comprising a combustion chamber having:

an air intake portion, and

means to discharge fuel into said chamber;

A blower assembly connected to and operated by said engine, and adapted to supply air under pressure to said intake portion;

A control circuit adapted to control the operation of said burner;

A source of control current adapted to supply current to said control circuit;

A tank adapted to retain water and to receive snow;

Said burner being adapted to heat said water and to melt said snow when said blower assembly is in operation and current is supplied to said control circuit;

Means to supply said current to said circuit only when predetermined factors are present;

Said last-mentioned means including:

A switch adapted to operate when said Water has substantially attained a level inconsistent with proper operation of said burner.

18. A snow melter as defined in claim 16, and further characterized by:

Means adapted to initiate the operation of a pump to evacuate said water, when said last-mentioned switch is in operation.

19. A snow melter as defined in claim 17, and further characterized by:

Means to initiate the stopping of said engine when said last-mentioned switch is in operation; and

Means to delay said stopping of said engine until said operation of said switch has been maintained a sulficient time to indicate that said water has in fact accumulated to said level.

20, A snow melter as defined in claim 18 and further characterized by:

A switch adapted to operate when said water has substantially attained a level inconsistent with proper operation of said burner;

Means to initiate the stopping of said engine when said last-mentioned switch is in operation; and

Means to delay said stopping of said engine until said operation of said switch has been maintained a suicient time to indicate that said water has in fact accumulated to said level.

21. A snow melter as defined in claim 19 and further characterized by:

Means to signal the operator when said last-mentioned switch is in operation, and before the stopping of said engine.

22. A snow melter comprising:

A burner assembly having: n

An engine depending upon electrical current for its operation;

An engine-operated source of current deriving power from said engine and adapted to supply electricity thereto;

A burner comprising a combustion chamber having:

an air intake portion, and

means to discharge fuel into said chamber;

A blower assembly connected to and operated by said engine, and adapted to supply air under pressure to said intake portion;

A control circuit adapted to control the operation of said burner;

A source of control current adapted to supply current to said control circuit;

A tank adapted to retain water and to receive snow;

Said burner being adapted to heat said water and to melt said snow when said blower assembly is in operation and current is supplied to said control circuit;

Means to supply said current to said circuit only when predetermined factors are present',

Said last-mentioned factors including:

The level of said water being in predetermined relation to said burner.

23. A snow melter as defined in claim 22 and further characterized by:

Said last-mentioned means including:

an engine-temperature switch adapted to operate when said engine has attained a normal operatin T temperature;

an air-pressure switch responsive to said air under pressure, and adapted to operate when said pressure is sufficient to support a ilame in said combustion chamber;

an oil pressure switch adapted to operate when the oil pressure in said engine falls below a safe level;

means to initiate the stopping of said engine, and substantially simultaneously to terminate the supply of current to said control circuit;

means to delay the stopping of said engine for a sufcient time following the termination of supply of control circuit current, to permit said air under pressure to purge said burner;

means to delay the supply of fuel to said burner subsequent to the termination of supply of control circuit current, until said burner has cooled below fuel-ignition temperature;

an engine temperature switch adapted to operate when said engine has attained a temperature substantially close to the upper limit for safe operation;

a thermal switch adapted to operate when the temperature of the burner upflow of the flame is above a normal degree;

Said burner having:

a main fuel valve,

a main fuel outlet,

a pilot fuel valve, Y

a pilot fuel valve,

an electrically operated ignitor disposed in the vicinity of said pilot fuel outlet,

a ame monitor adapted to indicate electrically whether a ame is present in the vicinity of said pilot fuel outlet;

Said blower assembly adapted selectively to convey air at full speed and at reduced speed, to said main fuel and pilot fuel outlets;

Said control circuit comprising:

Said generator supplying and a common line;

A relay coil connected to and energized by said current supplied by said generator;

A normally open switch adapted to be closed by the energization of said relay coil, and disposed in Series with said main fuel valve and a feeder line;

A normally open switch disposed in series with said blower assembly and said feeder line, and adapted when closed to establish full speed operation of said blower, and when open to establish reduced speed operation of said blower, said switch being adapted to be closed by the energization of said relay coil;

A relay coil B connected at one portion to said common line, and at another portion to a switch controlled by said flame monitor whereby when said flame monitor indicates the presence of a flame in the vicinity of said pilot fuel outlet, connection is made to said hot line, thereby energizing said relay coil B;

A normally open switch adapted to be closed by the energization of relay coil B, and disposed in series with said hot line and said feeder line.

current in a hot line References Cited UNITED STATES PATENTS 2,748,844 6/1956 Gilchrist, 158-28 X 2,815,068 12/1957 Forney et al. 158-28 3,052,231 9/1962 West et al. 126-3435 3,309,798 3/1967 Devlin et al. 126-3435 X CHARLES J. MYHRE, Primary Examiner. 

